In the prior art a very wide variety of kinds and compositions of multi-layer film arrangements are known to be used. Such film arrangements are employed typically for any of a very wide variety of purposes, including, for example, as carriers for an adhesive article. A feature common to these conventional film arrangements is that they are to be highly uniform and planar in formation, in order, for example, to avoid fluctuations in optical properties (transparency), in surface roughness, etc.
Known film arrangements may comprise, for example, unoriented films made from thermoplastics. These films can be extended by tensile stress. The product is a film having a greater length, a lower thickness, and, in general, a lower width. The film remains substantially flat. Where the film is composed of a partially crystalline thermoplastic, such as a polyolefin, the reduction in width and thickness is not uniform; instead, locally, there is formation of a constriction (neck-in) of high crystallinity, which increases further as extension continues. Following relaxation, the film continues to be flat (substantially two-dimensional), and has a lower width and thickness and a greater length than before the tensile test.